A memo released by House Intelligence Committee Democrats Saturday adds new pieces to the growing puzzle surrounding the FBI’s surveillance of a former adviser to President Donald Trump and its reliance on information paid for by Trump’s political opponents.

The memo directly contradicts some claims Republicans made in their own memo recently, offers mitigating information about others, and leaves at least one key allegation unaddressed.

At issue is an application to the Foreign Intelligence Surveillance Court to obtain an order for surveillance of former Trump adviser Carter Page in October 2016 and three applications to renew that order during the following year. The applications were signed off on by several top officials at the FBI and DOJ, and they were approved by four different judges who, as the Democratic memo notes, were appointed by Republican presidents.

Some of the evidence cited in the applications came from a dossier of reports compiled by former British intelligence officer Christopher Steele. Steele, who had been a reliable source for the FBI in the past, was looking into Trump’s Russia ties for Fusion GPS, a research firm being paid by an attorney for Democrat Hilary Clinton and the Democratic National Committee.

Earlier this month, House Intelligence Committee Chairman Devin Nunes, R-Calif., released a memo alleging that the FBI and DOJ misused political opposition research to target a Republican presidential campaign, misled federal judges, and abused the surveillance powers granted to them by the Foreign Intelligence Surveillance Act. President Trump authorized its release despite “grave concerns” from the FBI about its accuracy.

“FBI and DOJ did not ‘abuse’ the FISA process, omit material information, or subject this vital tool to spy on the Trump campaign,” the memo states, going on to defend the use of the dossier and detail additional facts that supported the investigation.

Republicans promptly released a response to Schiff’s response, claiming that the evidence presented by the minority did nothing to refute their premise.

Some legal experts say the Democratic response directly undercuts the central accusation of the Nunes memo that the FBI and DOJ did not sufficiently disclose Steele’s motivations to the FISC judge. Others say it confirms exactly what Nunes alleged.

“This is the first time I’ve ever seen FISA stuff played out this way,” said Robert Deitz, former general counsel for the National Security Agency.

How heavily did the FISA application rely on the dossier?

At this point, there is no dispute that investigators working on a counterintelligence probe of Russian interference in the 2016 election relied on information provided by Steele in an application for a FISA order on a former Trump adviser. How much they relied on it, however, is still very much in question.

According to Republicans, Steele’s information was a vital piece of the application, even though it was ultimately determined to be “minimally corroborated.” In their response to the Democratic memo, they quote a criminal referral by Sens. Chuck Grassley and Lindsey Graham that states Steele’s accusations made up “the bulk of the application.”

The Democrats claim investigators made only “narrow use” of the dossier’s allegations about Page’s trip to Moscow. It cites several other factors that supported the application, including the broader Russian election interference campaign, Russian outreach to the Trump campaign, Page’s history with Russian intelligence, and his suspicious activities in 2016.

Page is a relatively minor player in the narrative compiled by Steele, only mentioned in a few of the intelligence reports included in the 35-page document, and he is not linked to its most salacious claims. Steele’s allegations about Page specifically relate to two meetings during his visit to Moscow in July 2016.

According to Steele, Page met secretly with Putin associates Igor Sechin and Igor Diveykin, discussing possible lifting of Ukraine-related sanctions with Sechin and the Kremlin’s possession of compromising information about both Clinton and Trump with Diveykin. The existence of those meetings has never been publicly confirmed and Page denies having those conversations.

“Somehow Mr. Nunes and others have tried to raise the argument that in order to get a FISA order, one needs to have sort of jury-admissible evidence,” said Deitz, now a professor at George Mason University. “That’s not true. It’s never been true. It’s not true for a normal search warrant.”

Did the FBI have good reason to be suspicious of Carter Page?

Both sides largely agree that Carter Page had deep ties to Russia but a very limited role in Trump’s campaign. He was part of a foreign policy team that only met once and he missed that meeting. By the time surveillance on him began in October 2016, he was no longer involved in the campaign at all.

Page lived in Moscow from 2004 to 2007, he sought business deals with a state-owned energy company, and he was targeted at some point for recruitment by Russian intelligence. He was interviewed several times between 2013 and March 2016 by the FBI about those recruitment efforts.

Democrats say this is proof the FBI’s concerns about Page “long predate” Steele’s input. Republicans say it is an unfair depiction of a cooperating witness who helped the FBI prosecute the Russians who tried to recruit him. They also note that the Kremlin recruiters dismissed Page as “an idiot” in recorded conversations.

Whatever other suspicions the FBI had, Republicans say Steele’s dossier was still the only evidence they had of Page meeting with Kremlin-linked Russians in Moscow in 2016. Democrats maintain that Steele’s information was “consistent with the FBI’s assessment” of Page and his Russian ties.

Did the FISA applications disclose Steele’s ties to Clinton and the DNC?

What is not contested is that Steele was hired by Fusion GPS to investigate Trump’s ties to Russia on behalf of a law firm that represented the Clinton campaign and the DNC. Disagreement remains on whether the judge was properly informed of that connection and whether Steele himself knew who was paying for his services.

Republicans claimed in their memo that the FISA application obscured Steele’s ties to the Clinton campaign. Democrats insisted the partisan motivations of Steele’s employers was clear enough, even if it did not name Clinton or the DNC.

The Democratic memo reveals exactly how a footnote in the application described Steele as being approached by a “U.S. person” (presumably Glenn Simpson of Fusion GPS) who was hired by “a U.S.-based law firm” (Perkins Coie) to research “candidate #1’s” (Trump) ties to Russia. It adds that Steele himself was never explicitly advised of the motivation for the research.

“The FBI speculates that the identified U.S. person was likely looking for information that could be used to discredit candidate #1’s campaign,” the application stated.

Was Steele a credible source?

Both memos concur that Steele’s relationship with the FBI was terminated in October 2016 because of his unauthorized disclosures to the media. Republicans cite a criminal referral submitted to the DOJ by Grassley and Graham that alleges Steele lied to the FBI about those contacts.

The Democratic memo does not directly address the claim that Steele lied, but it does state that all of the FISA renewal applications properly explain why his involvement with the investigation was terminated. At the time of the initial application, there is no evidence the FBI knew of his contacts with reporters.

According to Deitz, it is not unusual for a FISA application to rely to a degree on the track record of a source who has a history with the bureau.

“You’d say something like, ‘A person who’s provided reliable information in the past has informed us of the following,’ and then you’re off to the races,” he said.

Did the FBI cite Steele to corroborate Steele?

Republicans maintain that a Yahoo! News article was included in the FISA application to corroborate Steele’s information, even though Steele turned out to be one of the sources the reporters spoke to. Democrats say that article and a second one were offered as evidence that Page was denying the dossier’s claims.

Democrats also emphasize that Steele’s admission in court filings to speaking to Yahoo! did not include any specifics of which information in the article came from him.

Former federal prosecutor Andrew McCarthy calls the Democrats’ position “highly unlikely” in a National Review op-ed. One potential flaw in the argument that he points to is that the Yahoo! article does not include a denial from Page, just a refusal to comment.

McCarthy also quotes Grassley and Graham’s referral, which states the application claimed the information in the article “generally matches” Steele’s research but did not appear to be provided by him, language that suggests it was presented as corroboration.

Was Steele’s evidence ever independently verified?

Among the passages that remained redacted in the public version of the Democratic memo, potentially the most significant is three paragraphs on page 4 that purport to describe “additional information obtained through multiple independent sources that corroborated Steele’s reporting.” The few stray unredacted words suggest it has something to do with Page and senior Russian officials.

Republicans stated in their response that the central claims about meetings with Sechin and Diveykin “were uncorroborated by any independent source, and they remain unconfirmed.”

The Democratic memo also suggests the three renewals of the FISA order confirm the FBI did obtain important investigative information from surveillance of Page. What exactly they learned is redacted, although what is legible indicates the intelligence gathered contradicted Page's testimony before Congress.

“You can’t just go back and say, ‘Yeah, judge, see our first declaration. We want more,’” Deitz said.

What did Andrew McCabe say?

The Republican memo claimed FBI Deputy Director Andrew McCabe, who signed one of the FISA applications, testified that “no surveillance warrant would have been sought from the FISC without the Steele dossier information.”

“The Majority purposefully mischaracterizes both what is actually contained in the FISA applications and the testimony of former FBI Deputy McCabe before our committee in December 2017,” a senior Democratic official told the Daily Beast at the time, adding, “The Minority’s memo lays out the full facts.”

The redacted memo does not lay out the full facts. It does not mention McCabe’s testimony on this question at all, but committee member Rep. Jim Himes, D-Conn., maintained Sunday that McCabe’s answer was misrepresented by the majority.

"I was in the room. Devin Nunes was not in the room when Andrew McCabe was interviewed, and I will tell you that he did not say that," Himes said on “Fox News Sunday,” though he acknowledged McCabe did say the dossier was “important” to the application.

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Absent the public release of the FISA applications, a move legal experts say has no precedent, it may be impossible to say who is telling the truth about any of these issues. Amid dueling political memos, Deitz worries that the entire intelligence oversight process has been infected by partisanship.

“It’s distressing seeing this pissing contest between Democrats and Republicans,” he said, “and particularly seeing it play out so publicly…It worries me that what this is doing is having a corrosive effect on intelligence and the seriousness with which the American people will take it.”